1. Field of the Invention
This invention relates generally to an electrical insulating structure having high mechanical strength, and more particularly to a system employing the insulating properties of anodized aluminum to insulate a weld probe force gage from weld current damage.
2. Background Art
In resistance welding, a pair of axially opposed welding electrodes are employed to clamp two workpieces being welded together in a fixed position with a predetermined force, and are further provided for passing a welding current through the workpieces to form a weld nugget--the fused metal that unites the workpieces. Although resistance welding machines typically have means for presetting and achieving a desired weld clamping force, this setting may change during operation. Accordingly, a weld probe force gage is used to determine the clamping or "squeeze" force exerted by the two electrodes. Such a weld probe force gage is used to either preset the desired applied force prior to operation, or alternatively is used to periodically monitor the applied clamping force during operation to ensure that it is within specified tolerances.
In operation, such a weld probe force gage is first inserted between the two electrodes of a welding machine. The electrodes are then clamped onto force application surfaces (generally receiving pockets) of a force sensor body of the gage. By way of a strain gage, a hydraulic pressure gage, or other transducer, the applied force is determined.
Conventional practice dictates that the application of welding current be disabled while the weld probe force gage is being used to prevent damage to the probe caused by excessive weld current. Notwithstanding the foregoing, weld current is nonetheless sometimes applied between the electrodes. For example, weld current is sometimes accidentally applied by the operator while the force gage is being used. Further, particular welding machines are not equipped with a welding current disable feature, which makes activation of the welding event to close the welding jaws to measure the clamping force impossible without also initiating welding current.
To protect the force gage from damage due to inadvertent or unavoidable current flow, others in the art have taken the approach that such currents can be safely shunted through the probe. Accordingly, force gages have been constructed of highly conductive materials, such as copper alloys, which are believed to have the ability to safely carry the applied welding currents. However, force gages constructed from such alloys not only increases the weight of the probe, but its material cost as well.
Accordingly, there is a need to provide a weld probe force gage that reduces or eliminates one or more of the problems as stated above.